The present invention relates to a dot line printer and in particular to a spring-charged type dot line printer having a printing heat assembly in which a plurality of printing heads are linearly arrayed.
In a prior art dot line printer having a printing head assembly in which a plurality of spring-charged type printing heads are linearly arrayed, there is provided a single impact pulse generator which generates single type of impact pulse as a printing pulse. Conventionally, the single impact pulse generator is connected to all of printing heads.
However, a problem occurs that the printing density and response frequency in the center of printing heads in the printing head assembly is different from those in the vicinity of the opposite ends of the assembly since the printing characteristics in the former is different from that in the latter due to the fact that the pulse widths of the impact pulses are identical.
In order to overcome the afore-mentioned problem, the characteristics of the printing heads has been made uniform by providing magnetic members which change the magnetic circuit structures in the vicinity of opposite ends or by adjusting the printing springs. There is a problem in that the number of steps for adjusting the printing quality uniform is large.
It is an object of the present invention to provide a dot line printer which is capable of making the characteristics of the printing heads uniform and of remarkably reducing the number of steps of adjustment for the uniform printing quality.
In a first aspect of the present invention, there is provided a dot line printer having a printing head assembly including a plurality of printing heads which are linearly arrayed, is wherein said dot line printer comprises a plurality of impact pulse generators for generating impact pulses to be applied to said printing heads; and a plurality of drive circuits, each of which is electrically connected to corresponding said impact pulse generator and to corresponding group of divided printing heads for controlling the driving of the printing heads in response to the impact pulses generated in said impact pulse generators.
In a second aspect of the present invention, each of said drive circuits is electrically connected to a pair of two groups among grouped printing heads, the two groups being equally spaced from a central head in the printing head assembly on the both sides thereof.
In a third aspect of the present invention, the dot printer comprises two impact pulse generators and two drive circuits, the drive circuit corresponding to one of the impact pulse generator is electrically connected to one pair of two groups of printing heads which are in the vicinity of the opposite side ends of said printing head assembly, and the drive circuit corresponding to the other impact pulse generator is electrically connected to a group of the rest of the printing heads disposed in the middle position of said printing head assembly.
In the dot line printer, it is preferred that the impact pulse generated by said impact pulse generator is preset so that it has a different pulse width for different impact pulse generator.
In the dot line printer, it is preferred that the impact pulse is applied to the printing heads disposed in the vicinity of the opposite side ends of the printing head assembly has a pulse width which is shorter than that applied to the rest of the printing heads.